meson: build gallium nine state_tracker

v2: - set d3d_drivers_path instead of dri_drivers_path
    - Fix nine guard to check for all relavent gallium drivers
    - Link with libswdri and libswkmsdri when necessary
    - Fix pkg-config generation
    - Add missing comma

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
diff --git a/meson.build b/meson.build
index b804341..3e8ea7d 100644
--- a/meson.build
+++ b/meson.build
@@ -560,6 +560,24 @@
   with_gallium_xa = false
 endif
 
+d3d_drivers_path = get_option('d3d-drivers-path')
+if d3d_drivers_path == ''
+  d3d_drivers_path = join_paths(get_option('libdir'), 'd3d')
+endif
+
+with_gallium_st_nine =  get_option('gallium-nine')
+if with_gallium_st_nine
+  if not with_gallium_softpipe
+    error('The nine state tracker requires gallium softpipe/llvmpipe.')
+  elif not (with_gallium_radeonsi or with_gallium_nouveau or with_gallium_r600
+            or with_gallium_r300 or with_gallium_svga or with_gallium_i915)
+    error('The nine state tracker requires at least on non-swrast gallium driver.')
+  endif
+  if not with_dri3
+    error('Using nine with wine requires dri3')
+  endif
+endif
+
 gl_pkgconfig_c_flags = []
 if with_platform_x11
   if with_any_vk or (with_glx == 'dri' and with_dri_platform == 'drm')
@@ -1131,9 +1149,6 @@
   dep_lmsensors = []
 endif
 
-
-# TODO: nine
-
 # TODO: clover
 
 # TODO: gallium tests